DC-DC converter

• US 7,254,046 B2
• Filed: 07/16/2004
• Issued: 08/07/2007
• Est. Priority Date: 07/16/2003
• Status: Active Grant

• Current Assignee: DENSO Corporation, Nippon Soken, Inc.
• Original Assignee: DENSO Corporation, Nippon Soken, Inc.
• Inventors: Shigeoka, Keiji, Kawasaki, Koji, Yamashita, Tsuyoshi
• Primary Examiner(s): Easthom; Karl
• Assistant Examiner(s): BEHM, HARRY RAYMOND
• Application Number:
  US10/892,341
• Publication Number:
  US 20050047175A1
• Time in Patent Office: 1,117 Days
• Field of Search: 363 2112- 18, 363/39, 363/16, 363 24- 26, 363/20, 363/40, 363/41, 363/131, 363/15, 363/56.09, 363/59.06, 363/43, 363/34, 363/37, 336/170
• US Class Current: 363/21.12
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33569 having several active switching elements H02M3/3353 takes precedence
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y10S 323/908 Inrush current limiters

Abstract

In a DC to DC converter, first and second primary windings are magnetically coupled to a first secondary winding. Third and fourth primary windings are magnetically coupled to a second secondary winding. The first and second primary windings are magnetically coupled to the first secondary winding. The third and fourth primary windings are magnetically coupled to the second secondary winding. The first and third primary windings are coupled in series to form a first coil member. The second and fourth primary windings are coupled in series to form a second coil member. One end of the first coil member is coupled to the first positive power line. A first switching element is coupled between the first negative power line and the other end of the first coil member. A first capacitor is coupled between the first negative terminal and one end of the second coil member.

Claims

1. A DC to DC converter connected to first positive and negative power lines and second positive and negative power lines for transferring a DC voltage between the first positive and negative power lines and the second positive and negative power lines, said DC to DC converter comprising:

a magnetic circuit having a first primary winding, a second primary winding, a third primary winding, a fourth primary winding, a first secondary winding, and a second secondary winding, said first and second primary windings being magnetically coupled to the first secondary winding, said third and fourth primary windings being magnetically coupled to the second secondary winding, said first and third primary windings being coupled in series to form a first coil member, said second and fourth primary winding being coupled in series to form a second coil member, one end of said first coil member being coupled to the first positive power line;

a first capacitor coupled between the first negative power line and one end of the second coil member; and

a first switching element coupled between the first negative power line and a connecting point at which the other end of the first coil member and the other end of the second coil member are connected to each other.

2. A DC to DC converter according to claim 1, further comprising a clamp circuit having one and other terminals, said one terminal of the clamp circuit being coupled to the one end of the second coil member, the other terminal of the clamp circuit being coupled to the other ends of the first and second coil members via the connecting point, wherein said clamp circuit is configured to bypass a current flowing through the first switching element when the first switching element is turned off.

3. A DC to DC converter according to claim 2, further comprising a controller coupled to the first switching element and configured to execute periodically a charging mode operation to turn off the first switching element, thereby allowing the first capacitor to be charged, and a discharging mode to turn on the first switching element, thereby allowing the first capacitor to discharge.

4. A DC to DC converter according to claim 3, wherein said clamp circuit comprises a second capacitor coupled at its one end to the one end of the second coil member;

and a second switching element coupled at its one terminal to the other end of the second capacitor and at its other terminal to the other ends of the first and second coil members via the connecting point, and

wherein said controller is configured to execute periodically the charging mode operation to turn off the first switching element and to turn on the second switching element, thereby allowing the first capacitor to be charged, and the discharging mode to turn on the first switching element and to turn off the second switching element, thereby allowing the first capacitor to discharge.

5. A DC to DC converter according to claim 4, wherein, when said DC voltage is supplied through the first positive and negative power lines to the magnetic circuit, said magnetic circuit generating a first output current in the second secondary winding based on the DC voltage while the first switching element is off state, said magnetic circuit generating a second output current in the first secondary winding based on the DC voltage while the second switching element is off state.

6. A DC to DC converter according to claim 4, further comprising:

a third switching element coupled at its one end to the second negative line and at its other end to one end of the second secondary winding, the other end of said second secondary winding being coupled to the second positive line; and

a fourth switching element coupled at its one end to the second negative line and at its other end to one end of the first secondary winding, the other end of said first secondary winding being coupled to the second positive line,

wherein said controller is configured to execute periodically the charging mode operation to turn off the first switching element in synchronization with turning off one of the third and fourth switching elements and to turn on the second switching element in synchronization with turning on the other thereof, thereby allowing the first capacitor to be charged, and the discharging mode to turn on the first switching element in synchronization with turning on one of the third and fourth switching elements, and to turn off the second switching element in synchronization with turning off the other thereof, thereby allowing the first capacitor to discharge.

7. A DC to DC converter according to claim 5, wherein said controller is configured to change an on duty ratio of the first switching element and that of the second switching element within a predetermined range to set ripple components contained in each of the first and second output currents less than a predetermined level.

8. A DC to DC converter according to claim 4, further comprising a first voltage system coupled to the first positive and negative power lines and operating on a predetermined first DC voltage;

and a second voltage system coupled to the second positive and negative power lines and operating on a predetermined second DC voltage, said first DC voltage being higher than the second DC voltage.

9. A DC to DC converter according to claim 4, further comprising a first voltage system coupled to the first positive and negative power lines and operating on a predetermined first DC voltage;

and a second voltage system coupled to the second positive and negative power lines and operating on a predetermined second DC voltage, said first DC voltage being lower than the second DC voltage.

10. A DC to DC converter according to claim 8, wherein said first voltage system includes either a DC power supply or a DC load, and said first capacitor and said first switching element are coupled to the either the DC power supply or the DC load without interposing a current smoothing choke coil therebetween.

11. A DC to DC converter according to claim 8, wherein said second voltage system includes either a DC power supply or a DC load, further comprising a converting circuit coupled to the first and second secondary windings, said converting circuit being coupled to the second voltage system without interposing a current smoothing choke coil therebetween.

12. A DC to DC converter according to claim 8, wherein said controller is configured to change an on duty ratio of the first switching element to selectively execute a first power transfer mode to transfer power based on the first DC voltage from the fist voltage system to the second voltage system and a second power transfer mode to transfer power based on the second DC voltage from the second voltage system to the first voltage system.

13. A DC to DC converter according to claim 12, wherein, when executing the first transfer mode, said controller is configured to increase the on duty ratio of the first switching element if the second DC voltage is lower than a first target voltage, and to decrease it if the second DC voltage is higher than the first target voltage, and wherein, when executing the second transfer mode, said controller is configured to decrease the on ratio of the first switching element if the first DC voltage is lower than a second target voltage, and to increase it if the first DC voltage is higher than the second target voltage.

14. A DC to DC converter according to claim 8, further comprising a smoothing capacitor coupled to the first positive and negative power lines in parallel to the first voltage system, wherein said first voltage system comprises a DC power supply and a power supply switch connected to each other in series and coupled to the first positive and negative power lines in parallel to the smoothing capacitor, and

wherein, when the power supply switch is off state, said controller is configured to transfer power from the second voltage system to the first voltage system to precharge voltage based on the transferred power to the smoothing capacitor and to turn on the power switch after the precharge is completed.

15. A DC to DC converter according to claim 14, wherein, when precharging the smoothing capacitor, said controller gradually increases the voltage applied to the smoothing capacitor.

16. A DC to DC converter according to claim 5, further comprising:

a synchronous rectifying circuit coupled to the second positive and negative lines to execute a synchronous rectifying operation of the first and second output currents;

a current sensor configured to detect a current flowing through the first switching element,

wherein said controller is coupled to the synchronous rectifying circuit and configured to determine whether a load current in the synchronous rectifying circuit exceeds a predetermined value according to the detected current value at a predetermined timing, thereby permitting the synchronous rectifying operation when determining the load current exceeds the predetermined value.

17. A DC to DC converter according to claim 16, wherein said predetermined timing is a timing after a predetermine time has passed since the first switching element is turned on.

18. A DC to DC converter according to claim 17, wherein said predetermined time is set to be longer than a time for which an excessive resonant current flows through the first switching element in reversed direction.

19. A DC to DC converter according to claim 12, wherein, when executing the first transfer mode, said controller is configured to decrease a maximum value of the on duty ratio of the first switching element with an increase of the first DC voltage of the first voltage system.

20. A DC to DC converter according to claim 12, wherein, when executing the second transfer mode, said controller is configured to increase a maximum value of the on duty ratio of the first switching element with an increase of the second DC voltage of the second voltage system.